The present invention relates a plasma CVD (Chemical Vapor Deposition) method for forming or depositing a film on an external surface of a hollow object or good having an opening, and also relates to a plasma CVD device and an electrode which can be used in the above method.
Resin has been used as materials, of many kinds of containers which are used in a food field, a medicine field and others. The resin products have advantages such as a light weight, a high resistance against impact and a low cost. However, the container made of resin has a poor gas-barrier property, and therefore suffers from such problems that contents are susceptible to oxidation, and a gas such as a carbon dioxide gas in the contents is liable to be externally discharged. Since the container is relatively soft, it is liable to be damaged by the contact with another good.
In view of the above, it has recently been attempted to form a hard carbon film such as a DLC (Diamond Like Carbon) film on a surface of a resin container in view of the fact that the hard carbon film has good properties such as a good wear resistance and a good gas barrier property.
For example, Japanese Laid-Open Patent Publication No. 8-53117 has disclosed the following method and device. In these method and device, a container to be subjected to film deposition is arranged in a hollow external electrode. This hollow external electrode has an inner space which is geometrically similar to but is slightly larger than the container. An internal electrode having a thin rod-like form is inserted into the container through its inlet or opening. The internal electrode arranged in the container is used as a gas nozzle, from which a film material gas or deposition material gas is introduced into the container, and a high-frequency electric power for forming gas plasma is supplied across the inner and outer electrodes Thereby, the carbon film is formed on the inner surface of the container. According to the foregoing publication, in these method and device, a negative self-bias is generated on the external electrode extending along the outer surface of the container so that the film can be deposited uniformly on the inner surface of the container, and since the discharge region is narrow, gas exhausting can be performed efficiently, and a required amount of the deposition material gas can be small so that the productivity is high.
A plasma CVD device, e.g., shown in FIG. 9 is also used for forming a film such as a carbon film on an external surface of a deposition target object having a container-like form. This device has a vacuum chamber 1, which is connected to an exhausting device 11, and is kept at a ground potential. A plurality of rod-like internal electrodes 21 are arranged in the chamber 1, and are carried on an electrically conductive support member 21xe2x80x2. The internal electrodes 21 and the conductive support member 21xe2x80x2 are electrically isolated from the chamber 1. A matching box 22 and a high-frequency power source 23 are connected in this order to the internal electrodes 21 via the support member 21xe2x80x2.
The vacuum chamber 1 is connected to a gas supply portion 3 of the deposition material gas. The gas supply portion 3 includes a mass-flow controller, a valve and a gas source, which are not shown in the figure.
For forming the films by the above device on the outer surfaces of the container-like deposition target objects S, i.e., the hollow objects S having the openings S1, the deposition target objects S are put into the chamber 1, and are fitted onto the internal electrodes 21 for supporting the objects S by the electrodes 21, respectively. Then, an exhaust device 11 operates to reduce the pressure in the chamber 1 to a predetermined pressure, and the deposition material gas is introduced from the gas supply portion 3 into the chamber 1. Also, the high-frequency power source 23 supplies a high-frequency power for plasma formation to the internal electrodes 21 via the matching box 22 so that the material gas thus introduced is changed into plasma. Under the plasma thus formed, the film is deposited on the outer surface of each deposition target object S having the container like form. The batch processing is performed to deposit simultaneously the films on the deposition target objects S equal in number to the internal electrodes 21.
According to the plasma CVD method and device taught by the Japanese Laid-Open Patent Publication No. 8-53117, since the carbon film is formed on the inner surface of the container, an effect of preventing damages, which may be caused by contact with another object, cannot be achieved.
In the film deposition process using the plasma CVD device shown in FIG. 9, the internal electrode supplied with the high-frequency power has a thin rod-like form and has a diameter smaller the inner diameter of the opening S1 of the deposition target object. Therefore, a plasma sheath which is formed around the internal electrode with the object wall therebetween may not extend along the outer surface of the deposition target object in some cases depending on the form thereof, and thereby it may be difficult to form a uniform film on the outer surface. Since the discharging occurs entirely in the vacuum chamber, the exhausting efficiency is low, and a large amount of deposition material gas is required, resulting in a low productivity.
Accordingly, an object of the invention is to provide a plasma CVD method of forming a film on an outer surface of a hollow object having an opening, and, particularly a plasma CVD method which can form a uniform or substantially uniform film on the outer surface of the object independently of the shape of the object.
Another object of the invention is to provide a plasma CVD method of forming a film on an outer surface of a hollow object having an opening, and particularly a plasma CVD method which can form the film on the outer surface of the object with a good productivity.
Still another object of the invention is to provide a plasma CVD device for forming a film on an outer surface of a hollow object having an opening, and particularly a plasma CVD device which can form a uniform or substantially uniform film on the outer surface of the object independently of the shape of the object.
Yet another object of the invention is to provide a plasma CVD device for forming a film on an outer surface of a hollow object having an opening, and particularly a plasma CVD device which can form the film on the outer surface of the object with a good productivity.
A further object of the invention is to provide an electrode which can be used in the above method and device.
For achieving the above objects, the invention provides a plasma CVD method, a plasma CVD device and an electrode, which are described below and belong to a first type.
Plasma CVD Method of the First Type
A plasma CVD method for forming a plasma from a deposition material gas by supplying an electric power to the gas, and forming a film on an outer surface of a hollow object having an opening under the plasma, wherein an internal electrode to be arranged in an inner space of the hollow object and an external electrode to be arranged outside the object are prepared as electrodes for supplying the electric power for forming the gas plasma, the internal electrode being capable of selectively having a reduced form allowing passage of the electrode through the opening of the hollow object and an enlarged form predetermined in accordance with a volume and a shape of the inner space of the object, the internal electrode having the reduced form is inserted into the inner space of the object through the opening of the object before forming the film on the outer surface of the object, then is changed into the enlarged form and is kept within the object, and the electric power for forming the gas plasma is supplied across the internal electrode and the external electrode for forming the film on the outer surface of the object.
Plasma CVD Device of the First Type
A plasma CVD device for forming a plasma from a deposition material gas by supplying an electric power to the gas, and forming a film on an outer surface of a hollow object having an opening under the plasma, comprising:
an internal electrode to be arranged in an inner space of the hollow object and an external electrode to be arranged outside the object as electrodes for supplying the electric power for forming the gas plasma, and the internal electrode being capable of selectively having a reduced form allowing passage of the electrode through the opening of the hollow object and an enlarged form predetermined in accordance with a volume and a shape of the inner space of the object.
Electrode of the First Type
An internal electrode used in plasma CVD for forming a plasma from a deposition material gas by supplying an electric power to the gas, and forming a film on an outer surface of a hollow object having an opening under the plasma, the internal electrode being arranged in the inner space of the hollow object for allowing supply of the electric power for plasma formation across the internal electrode and an outer electrode arranged outside the hollow object, wherein the internal electrode can selectively have a reduced form allowing passage of the electrode through the opening of the hollow object and an enlarged form predetermined in accordance with a volume and a shape of the inner space of the object.
For achieving the above objects, the invention also provides a plasma CVD method, a plasma CVD device and an electrode, which are described below and belong to a second type.
Plasma CVD Method of the Second Type
A plasma CVD method for forming a plasma from a deposition material gas by supplying an electric power to the gas, and forming a film on an outer surface of a hollow object having an opening under the plasma, wherein an internal electrode to be arranged in an inner space of the hollow object and an external electrode to be arranged outside the object are prepared as electrodes for supplying the electric power for forming the gas, plasma, the internal electrode including an electrically conductive and flowable material capable of flowing between the inner and outer spaces of the object through the opening of the object, the internal electrode is formed by flowing the conductive and flowable material into the inner space of the object through the object opening before forming the film on the outer surface of the object, and the electric power for forming the gas plasma is supplied across the internal electrode and the external electrode for forming the film on the external surface of the object.
Plasma CVD Device of the Second Type
A plasma CVD device for forming plasma from a deposition material gas by supplying an electric power to the gas, and forming a film on an outer surface of a hollow object having an opening under the plasma, comprising:
an internal electrode to be arranged in an inner space of the hollow object and an external electrode to be arranged outside the object as electrodes for supplying the electric power for forming the gas plasma, the internal electrode including an electrically conductive and flowable material capable of flowing between the inner and outer spaces of the object through the opening of the object, and the internal electrode being formed by flowing the conductive and flowable material into the inner space of the object.
Electrode of the Second Type
An internal electrode used in plasma CVD for forming a plasma from a deposition material gas by supplying an electric power to the gas, and forming a film on an outer surface of a hollow object having an opening under the plasma, the internal electrode being arranged in the inner space of the hollow object for allowing supply of the electric power for plasma formation across the internal electrode and an outer electrode arranged outside the hollow object, wherein the internal electrode includes an electrically conductive and flowable material capable of flowing between the inner and outer spaces of the object through the opening of the object, and being flowed into the inner space of the object to form the internal electrode.